1. Field of the Invention
The present invention relates to a semiconductor device in which a lead frame having a die pad portion for mounting a semiconductor element thereon and a board mounting portion for mounting a circuit board thereon is sealed with a resin together with the semiconductor element and the circuit board.
2. Description of the Background Art
FIGS. 18A and 18B illustrate a structure of a conventional semiconductor device and are a longitudinal sectional view and a plan view which show a main part of the semiconductor device, respectively. A circuit board 5 having a circuit component 7 such as an IC mounted thereon through a solder bump 6 and a semiconductor element 3 electrically connected to the circuit board 5 through a bonding wire 8 are mounted adjacently to a surface of a plate-shaped lead frame 1. The circuit board 5 is fixed to the lead frame 1 through a bonding resin 4 and the semiconductor element 3 is fixed through a solder 2. Portions of the lead frame 1 where the semiconductor element 3 and the circuit board 5 are to be mounted are sealed with a sealing resin 9 together with the semiconductor element 3 and the circuit board 5. In FIG. 18B, the sealing resin 9 is shown with portions closer to the semiconductor element 3 and the circuit component 7 than the lead frame 1 omitted.
FIGS. 19A and 19B illustrate a structure of another conventional semiconductor device and are a longitudinal sectional view and a plan view which show a main part of the semiconductor device, respectively. In the semiconductor device, a surface of a circuit board 5 mounting a circuit component 7 thereon is coated with another coat resin 10 in such a stage that the circuit board 5 has not been mounted on the lead frame 1. Other structures are the same as those of the semiconductor device shown in FIGS. 18A and 18B. Also in FIG. 19B, a sealing resin 9 is shown with portions closer to a semiconductor element 3 and the circuit component 7 than the lead frame 1 omitted.
Since the lead frame 1 to be employed for the conventional semiconductor devices shown in FIGS. 18A and 18B and FIGS. 19A and 19B is generally plate-shaped, the anchoring effect of the sealing resin 9 is obtained with difficulty. Therefore, it is impossible to sufficiently suppress the generation of a stress due to a difference in a coefficient of linear expansion between the lead frame 1, the semiconductor element 3, the circuit board 5 and the sealing resin 9. There is a problem in that the stress acts on the semiconductor element 3, resulting in the generation of a crack on the semiconductor element 3 or the disconnection of the bonding wire 8.
Moreover, since the lead frame 1 is flat, the solder 2 and the bonding resin 4 flow out from a portion between the semiconductor element 3 and the lead frame 1 and a portion between the circuit board 5 and the lead frame 1 respectively and easily extend over the lead frame 1. Consequently, a contact area of the sealing resin 9 with the lead frame 1 is reduced. From this viewpoint, the adhesion of the sealing resin 9 to the lead frame 1 is deteriorated.
A first aspect of the present invention is directed to a semiconductor device comprising a lead frame including a die pad portion for mounting a semiconductor element thereon and a board mounting portion for mounting a circuit board thereon, and a resin for sealing the semiconductor element, the circuit board, the die pad portion and the board mounting portion, wherein the lead frame further includes an anchoring region having a higher anchoring effect for the resin than that of each of the die pad portion and the board mounting portion between at least the die pad portion and the board mounting portion.
A second aspect of the present invention is directed to the semiconductor device according to the first aspect of the present invention, wherein the anchoring region has at least one through hole penetrating through a surface and a back in the lead frame between the die pad portion and the board mounting portion in the lead frame.
A third aspect of the present invention is directed to the semiconductor device according to the second aspect of the present invention, wherein a plurality of through holes are provided.
A fourth aspect of the present invention is directed to the semiconductor device according to the third aspect of the present invention, wherein the through hole is provided around the board mounting portion.
A fifth aspect of the present invention is directed to the semiconductor device according to the second aspect of the present invention, wherein the lead frame is divided by a dividing portion into a first lead frame portion having the die pad portion and a second lead frame portion having the board mounting portion, and the dividing portion functions as the anchoring region.
A sixth aspect of the present invention is directed to the semiconductor device according to the fifth aspect of the present invention, wherein the first lead frame portion surrounds the second lead frame portion in three directions as seen on a plane.
A seventh aspect of the present invention is directed to the semiconductor device according to the first aspect of the present invention, wherein the anchoring region is also present in the vicinity of a side part of the die pad portion in such a direction as to partition the die pad portion and the board mounting portion.
An eighth aspect of the present invention is directed to the semiconductor device according to the seventh aspect of the present invention, wherein the anchoring region has a plurality of through holes penetrating through a surface and a back in the lead frame.
A ninth aspect of the present invention is directed to the semiconductor device according to the first aspect of the present invention, wherein the anchoring region has at least one trench concaved in the lead frame between the die pad portion and the board mounting portion in the lead frame.
A tenth aspect of the present invention is directed to the semiconductor device according to the ninth aspect of the present invention, wherein a plurality of trenches are provided.
An eleventh aspect of the present invention is directed to the semiconductor device according to the ninth aspect of the present invention, wherein the anchoring region has at least one through hole penetrating through a surface and a back in the lead frame.
A twelfth aspect of the present invention is directed to the semiconductor device according to any the second, third, fourth, eighth and eleventh aspects of the present invention, wherein a side surface of the through hole has first and second internal wall surfaces which are perpendicular to the surface of the lead frame and a third internal wall surface which is provided in parallel with the surface of the lead frame and serves to connect the first and second internal wall surfaces.
A thirteenth aspect of the present invention is directed to the semiconductor device according to the fifth aspect of the present invention, wherein a side surface of the dividing portion has first and second internal wall surfaces which are perpendicular to the surface of the lead frame and a third internal wall surface which is provided in parallel with the surface of the lead frame and serves to connect the first and second internal wall surfaces.
In the semiconductor element, for example, the lead frame further has a lead to be exposed from the resin and to function as an external connecting terminal.
In the semiconductor element, for example, the semiconductor element of the die pad portion and the circuit board of the circuit mounting portion are electrically connected to each other through a wire.
According to the first and ninth aspects of the present invention, a continuity of an interface of the lead frame and the sealing resin in a direction from the die pad portion toward the board mounting portion (or an opposite direction thereto) is interrupted in the anchoring region so that a stress to be applied from the sealing resin to the die pad portion is relieved. Accordingly, it is possible to prevent the crack of the semiconductor element or the disconnection of the bonding wire from being caused by the stress. A solder and a bonding resin which serve to fix the semiconductor element and the circuit board to the lead frame can be prevented from flowing out between the die pad portion and the board mounting portion. Consequently, the adhesion of the resin can be enhanced.
According to the second aspect of the present invention, the sealing resin communicates at the anchoring region from both sides of the lead frame between the die pad portion and the board mounting portion in the lead frame. Therefore, the anchoring effect of the sealing resin can be increased.
According to the third aspect of the present invention, it is possible to further increase the anchoring effect in the semiconductor device according to the second aspect of the present invention.
According to the fourth aspect of the present invention, it is possible to further increase the anchoring effect in the semiconductor device according to the third aspect of the present invention.
According to the fifth aspect of the present invention, the die pad portion and the board mounting portion are divided in the lead frame and the dividing portion functions as the anchoring region. Therefore, it is possible to obtain the anchoring effect of the semiconductor device according to the second aspect of the present invention.
According to the sixth aspect of the present invention, the anchoring region is also present in the portion extended in the direction from the board mounting portion toward the die pad portion (or the opposite direction thereto). Therefore, it is possible to further increase the anchoring effect in the semiconductor device according to the fifth aspect of the present invention.
According to the seventh and eighth aspects of the present invention, the anchoring region is present not only between the die pad portion and the board mounting portion but also in the vicinity of the side part of the die pad portion in such a direction as to partition the die pad portion and the board mounting portion. Therefore, it is possible to further increase the anchoring effect in the semiconductor device according to the first aspect of the present invention.
According to the tenth or eleventh aspect of the present invention, it is possible to further increase the anchoring effect in the semiconductor device according to the ninth aspect of the present invention.
According to the twelfth aspect of the present invention, it is possible to further increase the anchoring effect in the semiconductor device according to the second, third, fourth, eighth and eleventh aspects of the present invention.
According to the thirteenth aspect of the present invention, it is possible to further increase the anchoring effect in the semiconductor device according to the fifth aspect of the present invention.
It is an object of the present invention to provide a semiconductor device capable of enhancing the adhesion of a sealing resin to a lead frame, thereby preventing the crack of a semiconductor device to be mounted on the lead frame and the disconnection of a bonding wire.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.